Hi Meghan,
I've always considered Neil Armstrong's "Shutdown" as the first word spoken
on the moon. That was not transmitted to Earth but was recorded on the
onboard-voice recorder. If you'd like to see the full transcript it's on the
Apollo Lunar Surface Journal, here:
http://www.hq.nasa.gov/alsj/a11/a11.landing.html

<<102:45:43 Armstrong (on-board): Shutdown>>

(Note that as you read the Journal, words in [brackets] are notes from the
Journal's creator, Eric Jones, or quotes from his interviews with the
astronauts, or quotes from transcribed post-mission debriefings.)